High intensity lighting projectors

ABSTRACT

A high intensity light projector for stage, architectural and similar applications includes a controllable image quality projection gate providing advanced visual effects. The projection gate, capable of selectively scattering or transmitting incident light, may be constructed of an array of scattering liquid crystal material in combination with infrared and ultraviolet reduction means which provide in the high intensity beam, a stable thermal environment by minimizing the absorption of light by the projection gate. Additional thermal efficiency is provided by supplemental cooling means. Color control is also provided in the form of dichroic filter wheels forming cooperating adjustable low, high and band width filters including saturation control. A color measuring feedback sensor is also provided. An intensity measuring feedback sensor controls a spatially-modulated, variable-density, reflectively-coated dimming wheel. A programmable gobo system has provisions for gobo selection, orientation, and rotation.

BACKGROUND—FIELD OF INVENTION

[0001] The present invention relates to light projectors used forvarious illumination and lighting applications and in particular toprojectors that are used to obtain visual effects, light patterngeneration and projection in stage illumination and in architectural,display and similar applications.

BACKGROUND AND DISCUSSION OF PRIOR ART

[0002] Lighting projectors, e.g., those used in stage lighting, aretypically equipped with one or more control devices for controllingintensity or focusing or dimensioning the beam, changing its color, orchanging the beam's direction. Modern multiple parameter (automated)projectors include controls for all of these parameters and more.

[0003] Although such projectors perform effectively in manyapplications, they suffer from a number of limitations which, ifovercome, could greatly expand the visual effects achievable by thelighting instruments and extend their utility to other environments. Toachieve such advances, improvements are required in the beam formingmechanism, in the projection of patterns, in the management of heatassociated with the light source, in the control of beam color, and inthe noise levels which derive from present cooling techniques. To beeffective, these improvements must function in a densely packed, compactand sometimes highly mobile structure housing both very fragile opticaland electronic components together with a light source capable ofproducing oven-like temperatures. (An exemplary application involving anominal image size of 10 ft. by 10 ft. (100 square feet) calls forbrightness in the neighborhood of 100 foot candles thus requiring theprojector to produce about 10,000 Lumens.) Moreover, certain types oflighting instruments go on “tour” and must withstand truck transportabuses and the vagaries of the weather.

[0004] A number of lighting control applications call for controllablebeam shapes and patterns. Performance lighting in stage productions, forexample, often requires a variety of different beam patterns and/orshapes. For this purpose, a projection gate is often used to form thedesired image across the beam of light. Typically, the projection gatesare embodied as shutters or etched masks that function like stencils inthe beam path to project a particular beam configuration. Knownarrangements, “gobos” for example, often include rotary assemblies thatincorporate several pattern generating elements encircling the axis ofrotation, along with a drive mechanism for rotating a selected patterninto the beam path.

[0005] In such arrangements only a limited number of patterns areavailable, there is no grey scale, and resolution is also limited.Another inherent limitation in this type of system, associated with itsdependence on physical motion, is the rapidity with which a desiredpattern can be selected and implemented.

[0006] Arrays of liquid crystal pixels are potentially useful asprojection gates because of their electro-optic effect, and because avirtually unlimited number of high resolution images may theoreticallybe synthesized quickly and easily.

[0007] Such liquid crystal arrays can be used to create images byselectively placing each individual pixel of the array in a relaxed(light blocking) state, or in an aligned (light transmitting) state, orin a state intermediate between the two extreme positions according to a“grey scale”. Selection of a grey level may be obtained by controllingthe voltage or other control stimuli that is applied to the pixel, thuscontrolling the alignment or transmissivity of the associated liquidcrystals. Over certain ranges there is a predictable relationshipbetween the applied control stimulus and the extent of alignment amongthe liquid crystals in the pixels, thus providing grey scale control.Whether used in this manner or in a two-state, on-off mode, pixellatedliquid crystal arrays have the potential to be used in a “light valve”capacity to create a complete picture across a beam of light.

[0008] Pixels in an array of liquid crystals may be relatively denselypacked thus offering opportunities for higher resolution andtransmission efficiency. Also, they may be individually controlled by anaddressing scheme capable of selectively placing each pixel of the arrayin a desired state. Thus a virtually limitless range of images may berapidly varied. In many applications pixels are arranged in a row andcolumn configuration and activated by applying a potential to aparticular control element associated with each of the pixels.Alternatively, a multiplex or other addressing scheme can be employed toreduce the number of elements necessary to address the pixels. Bothactive and passive matrices may be utilized.

[0009] Certain types of liquid crystal arrays have been previously usedwith some success in image projection applications. Arrays of twistednematic liquid crystal (TNLC) have been used and have provided severaladvantages over other image forming techniques. However, TNLC devicestypically require pre-polarization of incident light. Since a polarizerhas to be placed in the optical path to polarize the light before itreaches the TNLC gate, there is a loss of intensity of more than fiftypercent before it even reaches the array. In high intensity projectorsfor stage lighting and the like, this loss is far beyond acceptablelevels.

[0010] There have been efforts to address the light loss problem. Animproved method of illuminating a TNLC light valve with linearlypolarized light is discussed in “Large-screen Projection Displays II” byWilliam P. Bleha, Jr. (S.P.I.E. Vol. 1255, 1990). The disclosed methodfor converting unpolarized light into linearly polarized light is saidto double the intensity realized by conventional polarizers.

[0011] The disclosed polarization method uses a polarization convertorconsisting of a polarizing beam splitter, a polarization directionrotator and a synthesizer to significantly improve the illuminationefficiency. The polarizing beam splitter separates the incident lightinto two mutually perpendicular linearly polarized beams (transmittedp-polarized light and reflected s-polarized light). The polarizationdirection rotator effectively recaptures much of the light that was lostin previous polarizing systems by rotating the polarization direction ofthe p-polarized light ninety degrees to equalize both polarizationdirections. Thereafter, the two components of the light are combined onthe liquid crystal by the synthesizer.

[0012] The polarization convertor may ultimately provide a conversionefficiency approaching 100%. However, reflection and absorption lossesin the polarization convertor components, plus the losses in thecontrast-enhancing sheet polarizer, presently result in an overall 20%loss of intensity as the unpolarized light is converted to a linearlypolarized beam.

[0013] There are other formidable barriers in addition to excessivelight loss. Conventional polarizers typically associated with liquidcrystal arrays lose light intensity through an absorption process.Unfortunately, absorption converts light energy into heat causing thetemperature of the gate and surrounding optics to rise to intolerablelevels. In performance and display applications, where projectortemperatures can reach combustible levels, this process of heatabsorption causes a thermal buildup which would greatly exceed thetemperature limits of the liquid crystal array.

[0014] Various cooling techniques have been proposed which haveattempted to alleviate the destructive thermal effects of radiant energyabsorption. U.S. Pat. No. 4,739,396 to Gilbert Hyatt, particularlycolumns 50 through 62 of this patent, discusses numerous coolingtechniques which have been proposed for use in light projectors. Seealso U.S. Pat. No. 4,763,993 issued to James H. Vogeley, et al.

[0015] Cooling by forced air is thought to be effective in someapplications because it is theoretically transparent to incident lightand does not reduce the amount of transmission. Unfortunately however,heat dissipation techniques which depend on fan operation and otherforced air cooling techniques can create noise levels which make thistechnique unacceptable for many performance and display applications.Air cooling also exposes optical elements to atmospheric contaminantswhich can compromise optical clarity and cause other problems.

[0016] Other heat control arrangements for use in lamp environments areknown which might serve to protect a liquid crystal gate. For example,improvements in the maintenance of a stable thermal environment in stageprojectors have also been proposed by providing a heat exchanger thatcirculates a cooled fluid through a component of the lamp system foradditional cooling. The cooled fluid acts in a heat sink capacity toabsorb heat and conduct it away from the heat intolerant devices.

[0017] These and related techniques for improving the thermalenvironment of an optical projector system have been described by GeorgeIzenour in U.S. Pat. Nos. 4,843,529 and 4,890,208. In those references,a multi-layer dielectric interference filter, otherwise known as adichroic “hot mirror”, and a liquid cell are placed in the light pathbetween the light source and the mechanical projection gate to removeenergy in the infrared region from the beam of light. The hot mirroraids the process of infrared filtering by reflecting “near” infraredenergy having wavelengths in the range of about 700 to 1500 nanometerswhile passing light in other regions. The water in the liquid cell iseffective in absorbing the “far” infrared energy in the 1.5 to 10micrometer region that is not reflected by the dichroic filter. Thewater cell is effective because it displays good transmissioncharacteristics for energy having shorter wavelengths (i.e., visiblelight).

[0018] The combination of the infrared-absorbing liquid cell and theinfrared-reflecting “hot mirror” removes infrared radiation from thebeam before it reaches the projection gobo. This process reduces theheating effects of the infrared energy and results in an overallincrease in the temperature stability of the optical apparatus.

[0019] These and other methods of cooling which can include combinationsof radiation, convection, and conduction have been employed in reducingthe heating effects in some lighting applications. However, thepractical utility of these techniques to protect heat absorbing,temperature sensitive liquid crystal light valves in the oven-likeenvironment of a high-intensity projector, has not been demonstrated.

[0020] Because of these environmental obstacles and the loss ofsubstantial light through the use of polarizers, the full potential ofliquid crystal optics in the projection fields of interest has notheretofore been realized.

[0021] A second class of liquid crystal devices is available which willscatter, rather than absorb incident light while in a blocking mode.These scattering liquid crystal arrays thus offer the potential for usein high-intensity projectors having high heat environments.

[0022] Descriptions of liquid crystal devices that will scatter incidentlight are found in U.S. Pat. No. 4,671,618 to Wu et al. and U.S. Pat.No. 4,688,900 to Doane et al. These patents disclose the use of PolymerDispersed Liquid Crystal (PDLC) arrays which are essentiallymicrodroplets of nematic liquid crystals dispersed in a polymer matrix.The PDLC material is formed by a process known as phase separation. Thistype of device will scatter incident light when the light encounters amismatch between the indices of refraction at the media boundaries thatare encountered by the light traveling through the matrix. This occurswhen the liquid crystals are in a non-aligned state; the mismatch at theboundary of the polymer matrix and liquid crystal material causes theincident light to be reflected, refracted, and thereby scattered.

[0023] A similar type of scattering material is described in U.S. Pat.No. 4,435,047, to James L. Fergason, which discloses a liquid crystalmaterial encapsulated in a containment medium. This device allows fortransmission of incident light when the indices of refraction arematched and the liquid crystals in the capsules are in an orderedalignment. Scattering or absorption of incident light results from themismatch of the indices of refraction and the distorted or curvilinearalignment of the liquid crystals in the containment medium.

[0024] When light-scattering liquid crystals are placed in an orderedstate, e.g., by application of an electric field, the incident lighttraveling in a direction parallel to the electric field will encounter avirtual match between the indices of refraction at the interface of theliquid crystals and the matrix. The matched indices allow for unimpededtransmission of the incident light in this ordered state. (Thermal,magnetic, optic and other energy sources may also serve to control thealignment of the liquid crystals in an array.) Over a range, the degreeof transmission is proportional to the intensity of the applied field,thus affording a grey scale mode of operation.

[0025] In addition to offering the ability to scatter rather than absorbincident light, light scattering gates offer the vitally importantproperty of not requiring pre-polarization of the light incident uponthe projection gate. This eliminates a light intensity loss which isprohibitive for many applications.

[0026] Although there is reduced absorption of light in the visibleregion, the absorption characteristics for these light scattering gatesare not as favorable at longer wavelengths. They are thus subject tothermal damage from absorption of infrared energy in the high-intensityenvironment of certain projectors.

[0027] Accordingly, unless provided with an effective cooling technique,the resolution, speed and image forming abilities of scattering liquidcrystal arrays can not be exploited in the environment of high-intensityproduction lighting devices.

[0028] It is accordingly an object of the invention to provide athermally protected lighting projector gate having the resolution,programmability and response time of a liquid crystal array.

[0029] It is a further object of the invention to provide a lightprojection system which exploits the considerable advantages oflight-scattering liquid crystal arrays while protecting such arrays fromheat damage.

[0030] It is a further object of the invention to provide precise beampattern control for use in lighting and animation applications byutilizing a dynamically variable projection gate with a diverseassortment of patterns for high speed image projection.

[0031] Yet another object of the invention is to provide improvedprojector cooling techniques that provide more stable thermalenvironments thereby permitting a broader range of beam control devicesto be used in high intensity light projectors. Improved cooling tominimize the potential discomfort that is ordinarily experienced by aperformer under bright lights is another object.

[0032] A further object of the invention is to create innovative andunusual visual lighting effects by jointly and individually utilizing adynamically variable liquid crystal projection gate and a gobo unit.

[0033] An additional aim of the invention is to provide a lightingprojector that operates in a closed environment, thereby improvingreliability, decreasing the risk of contamination and reducing the noiseemanating from the system.

[0034] Another goal of the invention is to provide color controlassemblies capable of controlling color parameters in a graduated mannerin order to accommodate the special characteristics of human colorperception.

[0035] A further object of the invention is to provide improved colorcontrol systems employing feedback supplied by a beam spectrum sensor.

[0036] It is another object of the invention to provide improved goboutilization including a wider range of effects incorporating both staticand dynamic patterns.

[0037] Another object of the invention is to provide improved dimmingmeans coupled with an intensity level feedback sensor.

[0038] Other objects and advantages of the invention will becomeapparent in the description which follows.

SUMMARY OF THE INVENTION

[0039] Generally, one aspect of the invention comprises a lightprojection system for lighting applications having one or more lightprojectors which include image forming means, at least one of theprojectors comprising: (1) a light beam source for generating a beamhaving an intensity suitable for lighting applications; (2) a projectiongate located to modulate the beam and having an addressable array oflight-scattering liquid crystal pixels capable of assuming transparentand opaque states; (3) a heat management system for protecting the arrayof liquid crystals from the heat generated by the beam; and (4) a sourceof image control signals connected to the array to control the states ofthe pixels to vary the image projected by the beam.

[0040] Another aspect of the invention features an image projectionsystem comprising: (1) a light beam source for generating a beam; (2) abeam modulation system including an addressable array of lightscattering liquid crystal pixels capable of assuming transparent andopaque states; (3) a heat sink for the array comprising a liquid cell inthermally conductive relationship to the array; and (4) a source ofimage control signals connected to the array to control the states ofthe pixels to thereby vary the image projected by said beam.

[0041] Yet another aspect of the invention relates to color control andcontemplates a light projection system for lighting applications havingone or more light projectors which include beam color control means, theprojectors comprising: (1) a light beam source for generating a beamhaving an intensity suitable for lighting applications; (2) a set ofcolor filter elements transposable relative to the beam; and (3) certainof the color filter elements comprising variable dichroic filteringmaterials configured such that filter cutoff and cut-on wavelengths areadjustable by positioning said elements.

[0042] In one form the filter elements are circular elements in whichthe hue parameters vary circumferentially and saturation varies in theradial direction. Thus rotation through the beam varies hue whileorthogonal movement laterally of the beam axis effects saturationcontrol.

[0043] According to a further feature of the invention, the colorcontrol system includes a color responsive feedback element such as alinearly variable band pass filter functioning as a spectrum analyzerwhich in conjunction with a photodiode array or other suitabletransducer, measures beam color and supplies accurate color measurementsignals to a color controller. This permits precise color matching amongluminaires.

[0044] According to another aspect of the invention, gobo selectingmeans are combined with gobo orientation control means to produce aselection of gobo effects involving both programmably oriented staticpatterns and the dynamic rotation of those patterns.

[0045] According to a further aspect of the invention, an intensitycontrol system includes an intensity feedback transducer, and a dimmingwheel having a spatially-modulated, variable-density, reflective coatingapplied thereon, cooperating with a local control system to producespecified output intensity levels.

BRIEF DESCRIPTION OF DRAWINGS

[0046] A more complete understanding of the present invention may be hadby reference to the following Detailed Description with the accompanyingdrawings, wherein:

[0047]FIG. 1 is a schematic side elevation view of the interior of alight projector showing certain features of the invention;

[0048]FIG. 2 is a schematic view of a portion of a liquid crystal arrayillustrating various states of liquid crystal droplets contained in apolymer matrix;

[0049]FIG. 3 is a schematic view of an embodiment of a liquid crystal(LC) projection array and an infrared absorbing and conductive coolingliquid cell assembly;

[0050]FIG. 4 is a schematic plan view of a programmablelight-scattering, active-matrix projection gate for use in the systemsof FIGS. 1 and 7;

[0051]FIGS. 5 and 5A are schematic side sectional and perspective views,respectively, of an embodiment of the LC projection array and liquidcell assembly;

[0052]FIG. 6 is a schematic side sectional view showing an alternateembodiment of a LC projection array and liquid cell assembly;

[0053]FIG. 7 is a schematic side elevation view of a part of theinterior of a light projector showing the preferred optical systemthereof;

[0054]FIG. 8 is a plan schematic view which illustrates one of the colorfilters forming the color control system of the invention;

[0055]FIG. 8A is a plan schematic view which illustrates the dot densityof the color filters forming the saturation control system of theinvention;

[0056]FIG. 8B is a plan schematic view which illustrates thespatially-modulated, variable-density, reflectively coated dimming wheelof the invention;

[0057]FIGS. 9A through 9G comprise a set of spectral transmission curvesillustrating certain properties of the color wheel system of theinvention; and

[0058]FIG. 10 is a schematic plan view of an alternate embodiment of aprogrammable rotatable gobo wheel assembly.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0059] As shown in FIG. 1, a light projector system includes a lamp 10and a reflector 12 that cooperate to focus a beam of light 50 upon aprogrammable light pattern generator or projection gate 14 containing aliquid crystal array and immersed in a filter/coolant liquid cell 20.The light source 10, e.g., a high intensity, 1000 Watt arc lamp, emitsradiant energy over a band including visible, infrared, and ultravioletwhich is then collected by the reflector 12 and directed as a beam ofunpolarized focused light 50 to the programmable image generator 14.

[0060] The pixels of the latter are energized via a driver 18 which iscontrolled in turn by the lighting control system 40 which may be of thetype shown in U.S. Pat. No. 4,980,806 to Taylor et al., incorporatedherein by reference.

[0061] To filter energy in the “near” infrared region (havingwavelengths between visible light and “far” infrared) before thosewavelengths reach the sensitive projection gate 14, a multi-layerdielectric interference filter 32 may be placed between the projectiongate 14 and lamp 10. The filter 32 incorporates an optical thin filmexhibiting dichroic properties that are chosen to reflect near-infraredwhile transmitting the shorter, visible wavelengths.

[0062] A lens system such as 16 is provided to collect the light that istransmitted straight through, and modulated by, the gate 14 and toproject the resultant image.

Projection Gate

[0063] The programmable light pattern generator 14 is comprised of anarray of liquid crystal pixels capable of scattering light in one modeand transmitting light in another mode. One type of scattering materialsuitable for such an array is nematic liquid crystals dispersed in apolymer matrix. The resultant is referred to as Polymer-Dispersed LiquidCrystals (PDLC). Nematic curvilinear aligned phase (NCAP) liquidcrystals, liquid crystal polymer composites (LCPC), nematic-cholestericliquid crystal diplays (NC-LCD), and polymer network liquid crystaldisplays (PN-LCD) would also be suitable. Also, a TN system that reducesir susceptibility and polarization losses sufficiently, and employs LCsystems with appropriate properties, may suffice for some applications.

[0064] Pixel elements comprised of nematic liquid crystals dispersed ina polymer film can be individually driven to one of several states. Inone state, light incident at a narrow angle about the perpendicular willbe transmitted through the pixel element, and will then be collected bythe lens system 16 for projection. In another state, transmission ofincident light is effectively prevented by utilizing the reflective andrefractive properties of light traveling through interfaces withmismatched indices of refraction to scatter the incident light. A greyscale is obtained by placing the liquid crystals in intermediate statesof alignment by control of the energizing signal, thus controlling theamount of transmissivity of light straight through the pixel.

[0065] As shown in FIG. 2, the gate array comprises liquid crystaldroplets 41 dispersed in a polymer matrix 42, which is positionedbetween two transparent plates 14 a and 14 b, containing an activematrix 14 e (FIG. 4). The control elements 14 d, one for each pixel,each apply the proper drive voltage to its respective pixel 14 c from asignal source V.

[0066] The liquid crystal materials used in PDLC arrays have two indicesof refraction, measured along perpendicular axes. The extraordinaryindex of refraction, n_(e), is measured along the liquid crystal's longaxis, and the ordinary index of refraction, n_(o), is measured along anaxis perpendicular to the axis of n_(e) Additionally, the polymer matrixcontainment medium has an index of refraction, n_(p), that is matched tothe extraordinary index of refraction, n_(e). (In some cases n_(e) ismatched to n_(p).) By controlling the relative values of theserefractive indices, incident light I_(i) may be transmitted or scattereddepending upon whether the light encounters matched or mismatchedindices of refraction as it travels through the interfaces of thepolymer matrix/liquid crystal combination.

[0067] When in the transmissive state, (as schematically indicated onthe right side of FIG. 2) more than 90 percent of the light that isincident upon the pixels will be transmitted at a narrow angle about theperpendicular.

[0068] Alternatively, when a pixel is placed in its light blocking orscattering state (as indicated on the left side of FIG. 2), the liquidcrystals are in a random alignment and the extraordinary index ofrefraction, n_(e), is no longer aligned in the direction of lightpropagation. The light will exit the projection gate in a random fashionwith respect to the surface of the element as suggested by the dashedvectors, and is no longer a narrow focused beam; “straight-through”transmission thus is effectively prevented. It should also be noted thatthere is a significant amount of “back scattering” in addition to theexpected “forward scattering”.

[0069] Although over 90 percent of the light will pass through thepixels when they are in a scattering mode, it will not be collected forprojection by the lens assembly 16 due to the wide scattering angles(both forward and reverse). Thus transmission of light is effectivelyand controllably reduced without utilizing an absorption process thatwould damage the projection gate.

[0070] For many applications, it is preferred to control the range ofindex matching in the pixels from an exact degree of matching to amaximum degree of mismatch. As a consequence, the light will be nearlycompletely transmitted in one state, partially transmitted in theintermediate states, and dispersed to such an extent in the off state asto put the pixel in an opaque condition.

[0071] In some applications it will be sufficient to operate the pixelsin just the two end states, transparent and opaque, to provide an on-offmode.

[0072] It is preferable to design the gate to provide high contrastratios, e.g., ratios of about 100:1 or greater.

[0073] The composition of the liquid crystal and polymer composite usedin the projection gate 14 and the electrical characteristics of theactive matrix control elements will determine the signal (amplitude,frequency and timing), and power requirements of the gate driver systemused to vary pixel excitation over a range from transparent throughopaque. The liquid crystal matrix must have the proper electricalcharacteristics so that the voltage drop occurs primarily across theliquid crystal material 41, rather than across the polymer matrixmaterial 42. Active matrices are described in many patents andpublications. See e.g, U.S. Pat. No. 4,818,981 to Oki et al.

[0074] Depending on the liquid crystal and polymer composite used informing the array, the control parameters can establish that the pictureelements are in a clear state having an ordered alignment (perpendiculartransmissive mode) under normal conditions with no energy applied, andin an opaque state having a random alignment (oblique transmissive mode)with the application of the appropriate electrical signal; or viceversa. The former type of array is known as “reverse mode” and isparticularly desirable in applications that require the liquid crystalmaterial to return to a clear state when power is lost.

[0075] Some alternate ways of controlling the alignment of the pixels inan array include the use of thermal, magnetic or electromagnetic(including optical) excitation as control stimuli. In particularapplications, these methods may be suitable for incorporation asalternate embodiments in order to control the alignment of the liquidcrystals.

[0076] To provide the appropriate control signal, the electronic drivercircuit 18, FIGS. 1 and 4, typically receives a video signal from thelighting controller 40 and selectively energizes individual elements ofthe array in accordance with the input video pattern by selectiveapplication to the appropriate rows and columns, M1 and M2 (FIG. 4),respectively. As a consequence, the desired image is created across theprojection gate 14 and modulates the light beam which is then collectedand projected by the lens system 16.

[0077] Following the techniques taught in U.S. Pat. No. 4,980,806, videoframes may be stored as cues, e.g., locally in the lamp, and supplied asdirected to the gate to produce animated and real-time type imaging. Asingle frame can also be manipulated through processing to producemultiple variations. Alternatively, a video communication link can beemployed to supply continuous video from a remote source.

[0078] The driver circuit 18 preferably accepts video signals that arerepresented by digital logic control signals, which are transmittedeither serially or in parallel, and is typically designed as amicroprocessor-compatible peripheral device meeting the interfacerequirements of the liquid crystal array 14.

[0079] Depending on the application, the gate elements may be arrangedin various configurations, e.g., in a 100×100 element array containing10,000 individual pixels and the associated electrical connections forapplication of the drive signal to each. Using a row and column matrixarrangement, 200 electrical connections could be used to access each ofthe pixels in a 100×100 element array by way of the associated activeelement. In this manner, the image data can be sent down the columns inorder to activate the desired pixels activated row by row.

[0080] Active matrices are obtainable from Optical Imaging Systems ofTroy, Mich. Specific driver designs will depend on the characteristicsof the gate. For illustrative features see e.g., the drivers SED1180F,1181F, 1190F and 1191F marketed by S-MOS Systems Inc. of San Jose,Calif.

[0081] In some cases, a matrix technique utilizing Plasma addressing maybe appropriate in lieu of conventional active-matrix addressingtechniques thereby eliminating the need for control element 14 d. Plasmaaddressing is described by Thomas S. Buzak in “A New Active-MatrixTechnique Using Plasma Addressing” (S.I.D. 90 Digest pp. 420-423). Thetechnique replaces the active matrix required to access each pixel withplasma-containing channels and offers a broad drive voltage range withmeans for accurately placing that voltage at a selected pixel. The broadvoltage range provided by plasma addressing allows LC materialsrequiring a large drive voltage to be placed in a selected stateaccording to the desired grey level.

[0082] Plasma addressing simplifies display fabrications by replacingthe conventional TFT control elements (14 d) with a selectivelyconductive channel of confined gas. The array is therefore comprised ofdrivers for accessing pixel columns, similar to a conventionaladdressing scheme, and a plasma channel for each row to latch the columnvideo data. The transmissivity of an individual pixel is controlled byapplying a data signal to the pixel by means of its column driver and bycontrolling the conductivity of the gas contained in the associatedchannel. Plasma, a highly conductive ionized gas, completes theelectrical circuit between the data line and ground. Thus, the signal onthe data column will only excite the liquid crystals in the pixel whenthe gas is in its conducting, plasma state.

[0083] A preferred embodiment of the present invention for highperformance applications includes a 200×200 element PDLC array in anactive matrix, the unit being configured as the projection gate of alight projector that is constructed as a three square inch “window”.Where more modest imaging performance is acceptable, the gate maycomprise an array of 35×35 pixels. Even with this reduced resolution,image variety and speed are markedly superior to mechanically controlledgobos.

[0084] For a more comprehensive description of PDLC technology seeLiquid Crystals-Applications and Uses, Volume 1, edited by B. Bahadurand published by World Scientific Publishers, New Jersey, 1990. (Adetailed discussion of PDLC technology is found in Chapter 14).

[0085] An informative description of PDLC materials and manufacturingprocesses useful in producing a preferred gate can also be found in U.S.Pat. No. 4,673,255 issued to Doane, West et al.

TEMPERATURE CONTROL

[0086] The operation of a projection array comprised of a liquid-crystaland polymer composite is temperature dependent. Projection gates formedof this material, e.g., PDLC, offer maximum transmission only for aspecific range of temperatures, so maintaining the projection gatewithin a stable operating temperature range is important.

[0087] The infrared and ultraviolet energy that would be absorbed by alight scattering LC gate from the beam of a high intensity light sourcesuch as 1000 watt arc lamp, is substantially greater than the LCmaterial can tolerate. Accordingly, the projection unit shown in FIG. 1includes a heat control system which incorporates infrared filteringcontrol mechanisms 20, and 32 to mitigate the rise in temperature andthereby prevent thermal destruction of the optical elements. Filteringcontrol mechanism 32 also serves to absorb ultraviolet energy that wouldchemically alter the liquid crystal display.

Liquid Cell

[0088] For dealing with long wavelength infrared (“far” infrared) thesystem includes a liquid filled cell 20 containing water and/or anotherappropriate fluid such as ethylene glycol. As seen in FIG. 3, the cellis formed of two parallel, spaced transparent walls 22 and 24 orthogonalto the beam axis. Side walls, not shown, and top and bottom plates 24 aand 24 b complete the enclosure. The liquid in cell 20 absorbs infraredenergy from the beam 50, while providing excellent transmissioncharacteristics at shorter, visible wavelengths.

[0089] Removal of heat from cell 20 is accomplished by circulatingliquid through cell 20 via an inlet 24 c and an outlet 24 d, FIG. 3.These are connected in a line 31, FIG. 1, of athermostatically-controlled liquid circulating system including a pump25, flow control switch 30 and radiator 26. The latter may preferably becooled by convection. A thermostatically-controlled, low-noise fan 28located to avoid intrusive noise may be used for some applications.

[0090] The flow switch 30 may also be instrumented to sense the flow ofliquid so that, should the pump fail or the system develop a leak, thiscondition may be sensed and signalled to an attendant. Alternatively,the sensed condition may cause the lamp 10 to be automaticallyextinguished to protect the array 14 and other optical devices beforeany thermal problems develop.

[0091] As a further measure, an expansion chamber may be provided aspart of the circulation system which can be placed relatively remotefrom the cell to accommodate hydraulic pressure surges within the liquidsystem and thereby reduce the risk of leaks.

[0092] The coolant system which may employ ethylene glycol or a mixtureof it and water, serves to prevent excessive temperatures in both thefiltering liquid cell 20 and in the gate 14 immersed therein. A hotmirror 36 on the incident face of the gate provides additionaltemperature control. The assembly is also provided with anti-reflectivecoatings 35 on the interior of front window 22, back window 24 and theliquid interface of gate plate 14 b to increase transmission efficiency.

Alternate Cell/gate Construction

[0093] A preferred embodiment of the gate/liquid cell is shown in FIGS.5 and 5A. It comprises a first sealed cylindrical chamber 60 forcontaining the infrared absorbing liquid 64, preferably optically clearultra-pure water. A flanged cylindrical, flexible boot 62, preferably ofsilicon rubber, forms the peripheral boundary of a sealed chamber 60having end faces formed by transparent front and rear windows 88 and 85.The silicon boot 62 provides for expansion and contraction as the waterchamber volume varies with temperature.

[0094] The front and rear windows 88, 85 of the cell 60, clamped inplace with the aid of retainer clips 80, may be comprised of a fusedquartz material and are preferably of a minimum thickness consistentwith structural needs.

[0095] Surrounding the filtering chamber 60 is a second annular chamber66 suitable for containing a coolant 68, and providing for maximumheat-transfer between the liquid 64 in the cell 60 and the coolant 68 inchamber 66. The coolant chamber 66 is defined by the cylindrical boot62, forming its interior periphery and an outer cylinder 72, withflanges 81, as shown in FIG. 5. This arrangement provides a mechanismfor the transfer of heat absorbed by the water 64 from the infraredabsorbing process, out of the liquid cell chamber 60 transferred acrossthe boot 62 boundary to the secondary fluid or coolant 68.

[0096] Means are provided for circulating the coolant 68 through thecoolant chamber 66. For this purpose, the coolant is circulated throughthe chamber 66 by means of the input and output channels 65 and 67, theformer being connected to the output of a radiator, such as 26, FIG. 1,so that the temperature of the-liquid crystal display is maintained.

[0097] In addition to cooling the liquid cell, the coolant providescooling of the projection gate array 79 having a front glass 78 and arear glass 88. This is achieved by placing the matrix assembly inthermal contact with the liquid in the filtering chamber 60 thusaccessing the coolant. To this end, the rear glass of the projectiongate can be formed as the front window 88 of the liquid cell.Additionally, anti-reflective coatings 87 can be placed on the front andrear surfaces of the liquid cell/projection gate assembly as shown inFIG. 5. This is done to minimize interface mismatches and thus reducesurface reflections as light passes from one medium to another.

[0098] The sealed nature of chamber 60 of the liquid cell minimizesturbulence and maintains the transparency of the water to preserve theclarity of an image formed in the beam by the liquid crystal array. Whenmounted in a panning and tilting head assembly suitable for use as anautomated stage lighting instrument, the liquid subsystem will be filledto an extent to maintain the requisite clarity with no appreciableturbulence or bubbles within the cell.

[0099] An alternate embodiment of the gate/cell assembly is shown inFIG. 6. As illustrated, the infrared absorbing liquid is contained in acylindrical enclosure 110 defined by a cylindrical peripheral wall 115and transparent, planar front and rear windows 112 and 131. A helicalchannel is formed in cylindrical wall 115 and is covered. by an outersleeve 123 to define a coolant path 122 having inlet and outlet ports120 and 121. The resultant coolant flow is designed to provideadditional temperature stability.

[0100] Communicating with the chamber 110 is an expansion chamber 125which includes a duct 133 extending into chamber 110. The transparentface 112 of the unit includes a light scattering array 111 sandwichedbetween the transparent plates 112 and 113. The array may be of any ofthe forms previously described. The coolant in chamber 110 may beselected such that its index of refraction matches the index associatedwith the front and rear walls 112 and 131.

[0101] The preferred embodiment of the optical system of the presentinvention is illustrated in FIG. 7. The disclosed “fold back mirror”assembly offers several benefits. In addition to solving problems ofspace constraints, this configuration offers additional surfaces whichmay be utilized by the infrared and ultraviolet filtering assembly. Byapplying “cold mirror” coatings to certain of the reflective surfaces,additional infrared energy may be removed from the beam of light.

[0102] In this embodiment, the projector lamp assembly 200 includes alamp 201, such as a Phillips MSR series arc lamp, which is energizedfrom a lamp supply 202 controlled via a local processor 285 from thesystem controller 203. These system components may be of the type shownin previously mentioned U.S. Pat. No. 4,980,806. The lamp supply 202 andother electronic components are cooled via coolant lines 202 a and 202 bconnected to the coolant system.

[0103] Lamp 201 is mounted in a reflector assembly 204 having areflective surface 209 and a coolant chamber 205 with an inlet 206 andoutlet 207. Coolant is circulated through the chamber via these portsunder control of the coolant system previously described.

[0104] As an alternate embodiment, the reflector assembly may have anexterior cold mirror coating on surface 209 and an infrared absorbingsurface applied to the interior distal surfaces 205A and 205B of chamber205. Infrared light incident on the cold mirror is transmitted throughit and is then partially absorbed by the coolant in chamber 205 andpartially by the infrared absorbing surface on its walls.

[0105] The beam projected from projection assembly 200 is incident on acold mirror and liquid coolant unit 210 having an interior coolantchamber 211 which is connected to the coolant circulating system viainlet port 212 and outlet port 213.

[0106] The mirror includes a glass substrate 216 on which is deposited amulti-layer dielectric interference filter 215, which reflects light inthe visible spectrum while passing infrared and ultraviolet wavelengths.Infrared energy passing through the filter 215 is partially absorbed bythe coolant in chamber 211 and partially by the infrared absorbingsurface 214 mounted on the back of the mirror assembly. This surface toois the beneficiary of the heat conduction provided by the circulatedcoolant. The ultraviolet energy is absorbed partially by the glasssubstrate 216.

[0107] The projected beam reflected from mirror unit 210 is converged ona color control assembly 221. Although arrays of liquid crystal pixelscan be used to create multi-color projected images, relatively complexmulti-path optical systems are normally required. To avoid this expenseand complication and some of the tradeoffs it requires, it is preferredto generate a single color beam through the use of dichroic filters andto concentrate the resultant filtered monochromic (single color) lighton the projection array. This approach is desirable because thecombination of dichroic filter features (discussed in a followingsection) has been found to yield extraordinary color control.

[0108] The color wheel assembly embodying these features includes threecolor wheels 220A, 220B and 220C that offer a continuous range of colorsaround their circumference (see also FIG. 8) Under control of the systemcontroller 203, each of the three wheels may be rotated to a positioncorresponding to a particular set of color parameters. This permitssmooth fades and other continuous variations not achievable inconventional assemblies, including variations in color center (hue) andcolor band width (saturation) of the light beam.

[0109] Each color wheel comprises a variable, all dielectric dichroicfilter that allows light of particular bands of wavelengths(corresponding to particular colors) to pass while reflecting the lightat other wavelengths. This variable thickness multi-layer optical thinfilm is designed to minimize absorbance and to operate at high opticalpower densities. Its composition includes layers of dielectric materialshaving different indices of refraction and thickness, these parametersbeing varied over the filter surface to produce continuously variablespectral responses.

[0110] Constructing the color wheels out of all dielectric materialsprovides significant benefits over metal-dielectric designs; namely,high power through-put with minimal absorbance and greatly enhancedenvironmental ruggedness. See “Optical Thin Films Users' Handbook” byJames D. Rancourt, published by Macmillan, and in particular section,3.7.3 and sections 4.4.2 through 4.4.5. Color wheels of the typedescribed herein can be obtained from Optical Coating Laboratory Inc. ofSanta Rosa, Calif.

[0111] The first color wheel 220A may be a variable short wave pass“edge” filter transmitting light of shorter wavelengths and attenuatinglight of longer wavelengths. As shown in FIG. 9A, this filter tends topass light having “blue” wavelengths, and the cut-off wavelength can bevariably extended continuously by rotating the wheel to a positionhaving a different, e.g., longer cut-off wavelength such that the edgeeffectively slides along the wavelength axis, passing light havinglonger wavelengths (greens and reds).

[0112] The second wheel 220B may be a variable long wave pass edgefilter transmitting light of longer wavelengths and attenuating light ofshorter wavelengths with a variable cut-off wavelength. As shown in FIG.9B, this filter passes light having “red” or long wavelengths, and heretoo the cut-off wavelength can be continuously varied, e.g., by rotatingthe wheel to a position having a shorter cut-off wavelength such that itwill pass light having shorter wavelengths (greens and blues).

[0113] The third wheel 220C, may be a variable band-reject filter thatwill stop wavelengths within a band defined by a variable upper andlower wavelength, and will pass light outside of this wavelength band.As shown in FIG. 9C, as the third wheel is rotated the stop bandeffectively slides along the wavelength axis.

[0114] The three-wheel system constitutes a complex variable filtersystem that offers significant improvements in color control. As shownin FIGS. 9D, E and F, additional variations are obtained by controllingthe color density, e.g., by a half tone, or dot density, or othertechnique, as shown in FIG. 8A, to provide continuously variablesaturation radially from the inner region to the perimeter of eachwheel, and by providing displacement means for progressively translatingthe color wheels out of the beam to expose these different saturationvalues to the beam. This feature, controlled by controller 203, FIG. 7,provides saturation control of the color whereby the ability to controlthe amount of white light that is mixed with the color is obtained.

[0115] In the preferred embodiment, the filters are continuouslyvariable dichroic, all dielectric elements.

[0116] An illustrative combined effect of all three wheels is shown inFIG. 9G which depicts the remaining spectral energy after 3 stages ofsubtractive filtration of a white light beam.

[0117] Each of the three wheels can be fabricated from a disk having acircular aperture 152 in the center thereof, with a clear area 154around the inner edge of the disk adjacent to the central aperture 152as shown in FIG. 8A, the clear area 154 offering no color filtration.The wheels can be translated across the beam path to position thecentral aperture 152 in the beam path to eliminate color filtration, andto eliminate any light loss due to reflection or absorption. The wheelscan also be translated across the beam path to position the color filterarea corresponding to the desired level of color density or saturationin the beam path.

[0118] The areas of maximum saturation, being fabricated near theperiphery of the color filter wheels (as shown in FIG. 8A), ispositioned such that a light beam of a given diameter incident upon thewheel intercepts a portion of the color filter having a more narrowrange of hue variation than a light beam of the same diameter incidentupon a corresponding area of lesser saturation. Therefore, maximumsaturation and minimum range of hue variation throughout the beamdiameter is achieved near the periphery of the color filter wheel.Translating the color filter wheel across the beam path, such that thelight beam intercepts the wheel at a position closer to the center ofthe wheel, increases both the amount of unfiltered light passing throughclear regions formed by the dot density pattern, and increases the rangeof hue variation within the beam diameter as the beam subtends a greaterangle upon the wheel, thereby decreasing the saturation of a given hue.

[0119] Each color filter wheel is further fabricated to include anencoder pattern 150 (FIG. 8A) at the periphery of the wheel. When readby an appropriate detector/decoder, the encoder pattern 150 enablesdetection of a change in angular position. A two-track quadratureencoder pattern as shown in FIG. 8A, when combined with an appropriatecounter/timer circuit and an index point, allows local processor 285 todetermine absolute angular position and rotational velocity fromincremental angular position and direction of rotation signals.Alternatively, an absolute position encoding scheme would allow thelocal processor to determine absolute angular position and rotationalvelocity more directly by well-known techniques utilizing multiplesensors and multiple-bit digital encoding. Each color filter wheel maybe mechanically coupled to a “rim-drive” arrangement acting upon theperiphery of each wheel to control angular positioning of the wheel, asshown in FIG. 7.

[0120] Following the color control unit 221, along the optical path is afield stop 225 which blocks stray light. An optional integrating lens230 homogenizes any color variation across the beam.

[0121] The beam then passes through a color wheel 275 (optional,discussed hereinafter) and then through a collimating lens 235 afterwhich it is reflected from a folding mirror 236. This arrangement servesto direct substantially parallel light rays on the liquid crystalmaterial of the projection array to maximize transmission efficiency andto achieve a suitable optical path profile. The mirror 236 can be inthermal contact with an additional cooling chamber (not shown) connectedin the circulating system.

[0122] The preferred embodiment of the projection gate 240 is the LCarray of FIG. 5. Additionally gate 240 may for some applications bemoveable in and out of the light path under control of a solenoid ormotor M1. This feature extends the lifetime of the LC array by removingit from the light path while not in use. Further, it reduces light losswhen the projector is in other modes.

[0123] In certain applications, particularly when using crystal arraysof minimum resolution, dramatic visual effects can be achieved by theincorporation of a gobo wheel which modulates the beam along with the LCgate. For this purpose, the system may include gobo wheel 251 which viamotor MG provides a number of fixed patterns or other optical effectsarranged around a common axis and one of which is selected by rotatingthe motor MG under control of system controller 203. The selectedpattern may further be rotated to a desired orientation within the beamby motor MO. Additionally, one of the positions of the gobo wheelpresents a clear aperture to the beam. The gobo wheel 251 and the LCgate 240 can be used in combination with one another or independentlyfrom one another in modifying the beam for the formation of images. Ifthe LC array is to be used alone, the gobo wheel is driven to its clearposition. (Alternatively, it may be retracted away from the opticalaxis.) Similarly, if the gobo wheel is to be used alone, the LC array 14is displaced out of the beam path.

[0124] Following image generation, the optical system includes a relaylens 250 and a contrast aperture 255. The contrast aperture stops allnon-parallel light scattered by the projection gate that is incident onthe relay lens to improve the contrast ratio of the projected image.

[0125] A zoom lens system 260 controlled via motor M2 is provided at theexit of the projector and is controlled by system controller 203 toprovide focus and magnification selection. Additionally, an intensitycontrol iris 265 may be incorporated in the system and controlled by thesystem controller 203 which drives motor M3. In some applications, aseparate drive motor may be provided for each of the zoom elements.

[0126] The projection assembly is controlled in pan and tilt by theservo drives P and T. The assembly may be contained in a sealed housing270. This technique helps to preserve the sterile environment of theprojector and limits the noise that may be generated by various movingcomponents. Further cooling can be accomplished by constructing the lamphousing 270 of the lighting system as a double wall system that carriescoolant, acts as a heat sink that convects and radiates heat away fromthe projector.

Intensity Control

[0127] An alternate mechanical dimming means for controlling theintensity of the beam output may take the form of a transparent diskhaving a reflective coating whose reflectivity varies along anappropriate path on the disk. The reflectivity along the path is varied,for example, by varying the density of a dot pattern in the mannerdescribed with respect to FIG. 8A for color wheels 220A, 220B, and 220C.The density variation and its locus are preferably selected to achieve asmooth, linear change in intensity while also facillitating a quicktransition from black-out to full brightness. Thus, as shown in FIG. 8B,the path may be in the form of a dimming wheel 222 having a spirallyvarying reflectivity. The wheel 222 may be fabricated to include acentral aperture 226 for passing undimmed, full intensity light. Thevariable density dot pattern formed as a light-attenuating reflectivecoating may begin with a clear area adjacent the aperture 226, andproceed with increasing density, and therefore increasing reflectivity,in a spiral path toward the periphery of the wheel, as shown in FIG. 8B.The outer region, near the periphery of the wheel, reflects all of thelight incident thereon, thereby dimming the beam to zero intensity.

[0128] By conjointly rotating the wheel and translating the wheel acrossthe beam path, the beam is made to intercept the wheel at various pointsalong the spiral path such that the intensity level can be smoothlycontrolled. Slow fades may be controlled very smoothly, especially atthe low intensity end of the spiral path, owing to the gradual increasein the density of the reflective coating. Careful design of the dotpattern improves the linearity of a fade over what can be achieved witha dimming iris, since linear movement of an iris actuating arm producesnon-linear change in intensity, especially as the iris approaches thezero-intensity or fully-closed end of travel.

[0129] By quickly translating the wheel across the beam path with littleor no rotation of the wheel, the intensity level can be quickly changedfrom zero to full, or from full to zero, by bypassing the graduateddensity areas disposed along the spiral path. By following the spiralpath, a controllable intensity ratio of up to 10,000:1 may be achieved.

[0130] The dimming wheel 222 is rotatable and translatable relative tothe beam path. The dimming wheel 222 may be mechanically coupled to a“rim-drive” arrangement acting upon the periphery of the wheel tocontrol angular positioning of the wheel, as shown in FIG. 7.Additionally, the dimming wheel can be fabricated to include an encoderpattern as discussed with respect to color filter wheels 220A, 220B, and220C. In this manner, when the encoder pattern is read by an appropriatedetector/decoder, the encoder pattern enables detection and processingof a change in angular position.

[0131] Alternatively, the dimming means may be formed on a linear striphaving a reflective coating whose reflectivity varies along its length.The reflectivity of the linear strip is varied by varying the density ofa dot pattern in the manner described above. The linear strip provides asmooth, linear change in intensity as it is moved laterally across thebeam path By making use of a suitable durable flexible substrate,thelinear strip dimming means could be wound upon two spools disposed oneither side of the beam path. Thereafter, the dimming strip may berolled or un-rolled across the beam path to control the output intensityof the luminaire.

Intensity Feedback

[0132] A light-sensitive electrical device, such as a photo diode orother suitable transducer can be used to sample the beam after it hasbeen subjected to dimming by an intensity control mechanism, andprovides intensity feedback signals to the local processor 285 forintensity control. In one embodiment, shown in FIG. 7, the intensityfeedback device 224 is positioned to sample the intensity of light afterthe intensity control wheel 222. The intensity feedback arrangementallows a luminaire to produce a specified level of illumination.Intensity feedback may be selectively disabled in the operating systemsoftware controlling the local processor, for example in instances inwhich the feedback sensor might be in the shadow of a gobo or otherprojected image.

Color Matching

[0133] A problem which arises in some applications involves colormismatch between luminaires. Lamp color calibration can vary with lamptype and can also change with time making it difficult to achieveprecise color match among the luminaires of a system. To address thisproblem, the system according to the invention includes a color sensoror spectrum analyzer 280 for quantifying beam color. It is implementedwith a linear variable filter 280 a, FIG. 7, which is located to samplethe beam after it has been subjected to coloring by the beam colorsystem 221. For this purpose, it may be located to receive a sampledportion of the beam which passes through an aperture 236 a of mirror236.

[0134] The linear variable filter, which may be of the type marketed byOptical Coating Laboratory, Inc. under the mark Selectraband (TM),provides a band pass filter having a center frequency which varieslinearly with spatial positioning. It can be combined with a suitable icphoto diode array 280 b to produce a composite signal indicative of thebeam's spectrum. This output can be processed as closed loop feedback,for example, by a local dedicated microprocessor Up or sharedmicroprocessor 285 which can also supply the measured color data to thesystem controller. The local or remote color controller circuits of thesystem can thus control the color system to produce a specific colorcondition. This provides the means for obtaining absolute coloraccuracies of the projected beams and also enables compensation fordifferences in the light source. Each luminaire is thus able toreproduce a desired color more precisely, even if the spectral output ofthe light source changes over time. A group of several luminaires isalso able to reproduce the same color more accurately, even if thespectral output of the several light sources varies from source tosource at a given moment.

Additional Sequential Color System

[0135] If real-time full color images are desired, they may be obtainedwith the present single-path optical system by sequentially illuminatingthe projection array with a plurality of primary colors, e.g. red, greenand blue. A monochrome system normally utilizes a frame rate ofapproximately 25 to 30 images per second to achieve the illusion ofcontinuous motion with virtually no flicker. In order to obtainsequential full-color operation, the frame rate of the present system isincreased to three times the flicker rate, with each frame consisting ofthree image fields, one for each of the three primary colors (e.g., red,green and blue)

[0136] During each frame, the projection array, e.g., array 79 of FIG.5, is addressed with the video information corresponding to the imagefield for the first of the primary colors and is then illuminated withthat selected primary color. As a result, the projection array willproject the video information for the image field of the first primarycolor during a first interval of the frame period. Thereafter, during asecond interval, the projection array is addressed with the videoinformation corresponding to the next image field and the array isilluminated with the light for the second primary color. This process isthen repeated for the third primary color. According to this procedure,the red, green and blue image fields are projected in sequence for eachframe. The full color moving image results as the human eye integrateseach of the primary colors together.

[0137] To obtain each of the primary colors required for sequentialfull-color operation, a dedicated tri-color wheel assembly 275, FIG. 7,can be included in the color control unit. Each sector of the wheel 275is a dichroic filter that passes light of certain wavelengths,corresponding to a desired color. The dedicated color wheel can serve tosimplify the color filtration operation necessary in achieving asequential full color system. Similar to the operation of the threecolor wheels 220A, 220B, 220C disclosed above, the dedicated tri-colorwheel 275 can be translatable out of the optical path to eliminate colorfiltration. (Note also that a white beam of ⅓ brightness could beobtained by spinning the wheel and not modulating the gate. Further,when a single color beam is needed, e.g., blue, the sequential systemwill have an intensity ⅓ that of a dedicated filter system) A sequentialcolor liquid crystal display system is found for example in U.S. Pat.No. 4,843,381 issued in the name of Yair Baron.

Programmable Rotatable Gobo Wheel

[0138] A preferred embodiment of the gobo wheel 251, discussed withrespect to FIG. 10, offers improvements in the automated orientation ofgobo patterns. To this end, a gobo carrier 325 supporting a set ofindividual gobo units 330 about its periphery may be rotated by a motorMG controlled by a Gobo Select System 390 to position a selected one ofthe gobos 330 at a site 361 within the path of the light beam passingthrough the gobo assembly.

[0139] Carrier 325 may be controlled by an open or closed loop analog,digital or hybrid motor control system which is constructed andcontrolled by the lamp mechanisms and lighting controller of previouslycited U.S. Pat. No. 4,980,806.

[0140] The orientation of each gobo unit 330 is also variable andadjustable. For this purpose, the gobo wheel assembly 325 includes a sungear 345 which engages gobo gears 335 incorporated around the peripheryof each gobo unit. Sun gear 345 is controlled by a Gobo OrientationController 391. It too may embody any of the drive systems used in theGobo Select System. In either or both systems, position, velocity andrelated parameters such as acceleration may be utilized.

[0141] Since the sun gear 345 engages all gobo gears 335 all the time,rotating any one gobo causes all gobos to rotate. By rotating gobocarrier 325 and sun gear 345 at the same time and by different numbersof degrees of angular displacement, any selected gobo can be rotated bythe sun gear to a desired orientation as it is being placed inprojection gate site 361 by the gobo carrier. The selected gobo canfurther be rotated continuously or intermittently as desired while inthe projection gate. The speed and direction of rotation of a gobo canalso be controlled.

[0142] At least one orientation of the sun gear relative to the gobocarrier will result in the gobo which is positioned in the projectiongate being in an “upright” orientation. In a preferred embodiment, therewill be at least as many such orientations of sun gear relative to gobocarrier resulting in upright orientations of the gobos as there aregobos, achieved by careful selection of gear ratios between sun gear andgobo gears. All of the gobos can be installed while the sun gear andgobo carrier are fixed in one such orientation so that subsequently theorientation of the gobos may be accurately and predictably controlled.When the gobo carrier and sun gear are rotated by an equal number ofdegrees of angular displacement and in the same direction of rotation,gobos are exchanged with the upright orientation maintained. By rotatingthe sun gear a certain number of degrees relative to the gobo carrier,the orientations of the gobos are altered a corresponding number ofdegrees. By rotating the sun gear a certain number of degrees more orless than the gobo carrier is rotated, gobos are exchanged and theirorientation altered at the same time. Alternatively, by carefulselection of gear ratios between sun gear and gobo gears, the gobocarrier may be rotated while the sun gear is held motionless, and theselected gobo “rolls” into position assuming the desired orientation asit comes to rest in the projection gate. With speed control applied tothe motor MG, the “rolling” effect may be used to creative advantage inthe design of animated lighting effects.

[0143] The disclosed gobo assembly and system offers accurate, flexibleand independent control of a wide range of beam pattern effects, bothstatic and dynamic for incorporation in lighting cues. By selectingcontinuous or intermittent gobo rotation unusual and dramatic visualeffects can be achieved.

1. An optical system for shaping a beam of light having an optical axis,comprising: a light beam source for generating an unpolarized beamhaving an intensity suitable for lighting applications; a projectiongate located to form a light beam shape and having an array of lightshaping pixels; each pixel being capable of assuming first and secondpixel states, further comprising: the first pixel state forming at leasta portion of a light beam shape, by causing at least a portion of thelight beam to propagate from the projection gate along the optical axis;and the second pixel state forming at least a portion of a void in thelight beam shape, by directing at least a portion of the light beam inone or more angles away from the optical axis, thereby substantiallyreducing absorption of the light beam by the projection gate and heatingof the projection gate by the light beam.
 2. The optical system of claim1, wherein the beam of light is at least partially transmitted to anobject of illumination in the light beam shape to project an image onthe object of illumination, the image being defined by the projectiongate and resembling a gobo pattern.
 3. The optical system of claim 2,wherein the light beam shape is capable of being dynamically varied suchthat the image resembles a plurality of gobo patterns.
 4. A lightprojector, comprising: a light beam source for generating an unpolarizedlight beam having an intensity suitable for lighting applications, saidlight beam propagating along a light beam path; a projection lensdisposed in said light beam path; a projection gate located to modulatesaid unpolarized light beam and having an addressable array of elements,said projection gate being disposed in said light beam path and beingilluminated by said light beam; wherein a plurality of elements of saidaddressable array of elements can be individually driven to at least twostates, comprising: one state in which light incident on the arraypropagates to said projection lens rather than being absorbed by saidelement; and another state in which light incident on the array isdeflected away from the projection lens rather than being absorbed bysaid element.
 5. The light projector of claim 4, wherein the projectiongate is located to form a light beam shape, and wherein the light beamis at least partially transmitted to an object of illumination in thelight beam shape to project an image on the object of illumination, theimage being defined by the projection gate and resembling a gobopattern.
 6. The light projector of claim 5, wherein the light beam shapeis capable of being dynamically varied such that the image resembles aplurality of gobo patterns.
 7. A light shape altering device, havingelements which selectively modify light, located in the path of a lightbeam and comprising: a first selective light reflection device, having aplurality of elements, each element defining a portion of an image, andeach element being separately controllable between a first state whichpermits light to travel to a desired object of illumination and a secondstate which reflects light away from the desired object of illumination;and a controller which obtains a desired shape and which converts saidshape into control signals for said first selective light reflectiondevice, so that said selective light reflective device permits light ofa predetermined shape to travel to said desired object of illumination.8. The light shape altering device of claims 7, wherein the firstselective light reflection device is located to form a light beam shape,and wherein the light beam is at least partially transmitted to thedesired object of illumination in the light beam shape to project theimage on the desired object of illumination, the image resembling a gobopattern.
 9. The light shape altering device of claim 8, wherein thelight beam shape is capable of being dynamically varied such that theimage resembles a plurality of gobo patterns.
 10. A light beam shapealtering device, having elements which selectively modify light, locatedin the path of a light beam and comprising: a first selective lightdeflection device, having a plurality of elements, each element defininga portion of an image, and each element being separately controllablebetween a first state which permits light to travel to a desired objectof illumination and a second state which deflects light away from thedesired object of illumination: and a controller which obtains a desiredshape and which converts said shape into control signals for said firstselective light deflection device, so that said selective lightdeflection device permits light of a predetermined shape to travel tosaid desired object of illumination.
 11. The light beam shape alteringdevice of claim 10, wherein the first selective light deflection deviceis located to form a light beam shape, and wherein the light beam is atleast partially transmitted to the desired object of illumination in thelight beam shape to project the image on the desired object ofillumination, the image being defined by the first selective lightdeflection device and resembling a gobo pattern.
 12. The light beamshape altering device of claim 11, wherein the light beam shape iscapable of being dynamically varied such that the image resembles aplurality of gobo patterns.
 13. A light projector, comprising: a lightbeam source for generating an unpolarized light beam having an intensitysuitable for lighting applications; a projection lens disposed toreceive and transmit said light beam to an object of illumination; and aprojection gate having an array of separately controllable elements tomodulate said unpolarized light beam to form one or more light beamshapes by selectively deflecting one or more portions of the light beamaway from the lens, substantially without absorption of the light beam.14. The light projector of claim 13, wherein the light beam is at leastpartially transmitted to the object of illumination in the one or morelight beam shapes to project an image on the object of illumination, theimage being defined by the projection gate and resembling a gobopattern.
 15. The light projector of claim 14, wherein the one or morelight beam shapes is capable of being dynamically varied such that theimage resembles a plurality of gobo patterns.
 16. A light projector,comprising: a light beam source for generating an unpolarized light beamhaving an intensity suitable for lighting applications, said light beampropagating along a light beam path; a projection gate located tomodulate said unpolarized light beam and having an addressable array ofelements, said projection gate being disposed in said light beam pathand being illuminated by said light beam; a projection lens disposed insaid light beam path and projecting an image of said projection gate asilluminated by said light beam; an active heat control system forprotecting said addressable array from the heat generated by said lightbeam; and a source of control signals connected to said addressablearray to control the states of said elements to modulate said lightbeam, wherein each of a plurality of elements of said addressable arrayof elements can be individually driven to one of a plurality of states,comprising: one state in which light incident on said element iscollected by said projection lens and projected as at least a portion ofsaid image; and another state in which incident light on said element isscattered at least in part by reflection and effectively prevented frombeing collected by said projection lens and projected as at least aportion of said image.
 17. The light projector of claim 16, wherein theprojection gate is located to form a light beam shape, and wherein thelight beam is at least partially transmitted to the object ofillumination in the light beam shape to project the image on an objectof illumination, the image resembling a gobo pattern.
 18. The lightprojector of claim 17, wherein the light beam shape is capable of beingdynamically varied such that the image resembles a plurality of gobopatterns.
 19. A light beam shape altering device, comprising: a lightbeam source for generating a light beam having an intensity suitable forlighting applications; a projection lens disposed to receive andtransmit said light beam to an object of illumination; and a projectiongate having an array of selectively controllable elements defining alight beam shape transmitted through the projection lens to an object ofillumination; and each of the elements comprising a light beam directiondeflection device selectively deflecting, instead of blocking, at leasta portion of said light beam in a direction away from the lens to formone or more opaque areas in at least a portion of the light beam,substantially without absorption of the light beam and resulting heatingof said projection gate.
 20. The light beam shape altering device ofclaim 19, the light beam is at least partially transmitted to the objectof illumination in the light beam shape to project an image on theobject of illumination, the image being defined by the projection gateand resembling a gobo pattern.
 21. The light beam shape altering deviceof claim 20, wherein the light beam shape is capable of beingdynamically varied such that the image resembles a plurality of gobopatterns.
 22. A light projector, comprising: a light beam source forgenerating an unpolarized light beam having an intensity suitable forlighting applications, said light beam propagating along a light beampath; a projection lens disposed in said light beam path and projectingan image of said projection gate as illuminated by said light beam; aprojection gate located to modulate said unpolarized light beam andhaving an addressable array of elements, said projection gate beingdisposed in said light beam path and being illuminated by said lightbeam, wherein each of a plurality of elements of said addressable arrayof elements can be individually driven to one of a plurality of states,comprising: one state in which light incident on said element iscollected by said projection lens and projected as at least a portion ofsaid image; and another state in which incident light on said element isscattered at least in part by reflection and effectively prevented frombeing collected by said projection lens and projected as at least aportion of said image; an active heat control system for protecting saidaddressable array from the heat generated by said light beam; and asource of control signals connected to said addressable array to controlthe states of said elements to modulate said light beam.
 23. The lightprojector of claim 22, wherein the projection gate is located to form alight beam shape, and wherein the light beam is at least partiallytransmitted to the object of illumination in the light beam shape toproject the image on an object of illumination, the image resembling agobo pattern.
 24. The light projector of claim 23, wherein the lightbeam shape is capable of being dynamically varied such that the imageresembles a plurality of gobo patterns.
 25. An optical system forshaping a beam of light having an optical axis, comprising: a light beamsource for generating an unpolarized beam having an intensity suitablefor lighting applications; a programmable light pattern generatorlocated to form a light beam shape and having an array of light shapingpixels; each pixel being capable of assuming first and second pixelstates, further comprising: the first pixel state forming at least aportion of a light beam shape, by causing at least apportion of thelight beam to propagate from the programmable light pattern generatoralong the optical axis; and the second pixel state forming at least aportion of a void in the light beam shape, by directing at least aportion of the light beam in one or more angles away from the opticalaxis, thereby substantially reducing absorption of the light beam by theprogrammable light pattern generator and heating of the programmablelight pattern generator by the light beam.
 26. The optical system ofclaim 25, wherein the beam of light is at least partially transmitted toan object of illumination in the light beam shape to project an image onthe object of illumination, the image being defined by the programmablelight pattern generator and resembling a gobo pattern.
 27. The opticalsystem of claim 26, wherein the light beam shape is capable of beingdynamically varied such that the image resembles a plurality of gobopatterns.
 28. A light projector, comprising: a light beam source forgenerating an unpolarized light beam having an intensity suitable forlighting applications, said light beam propagating along a light beampath; a projection lens disposed in said light beam path; a programmablelight pattern generator located to modulate said unpolarized light beamand having an addressable array of elements, said programmable lightpattern generator being disposed in said light beam path and beingilluminated by said light beam; wherein a plurality of elements of saidaddressable array of elements can be individually driven to at least twostates, comprising: one state in which light incident on the arraypropagates to said projection lens rather than being absorbed by saidelement; and another state in which light incident on the array isdeflected away from the projection lens rather than being absorbed bysaid element.
 29. The light projector of claim 28, wherein theprogrammable light pattern generator is located to form a light beamshape, and wherein the light beam is at least partially transmitted toan object of illumination in the light beam shape to project an image onthe object of illumination, the image being defined by the programmablelight pattern generator and resembling a gobo pattern.
 30. The lightprojector of claim 29, wherein the light beam shape is capable of beingdynamically varied such that the image resembles a plurality of gobopatterns.
 31. A light projector, comprising: a light beam source forgenerating an unpolarized light beam having an intensity suitable forlighting applications; a projection lens disposed to receive andtransmit said light beam to an object of illumination; and aprogrammable light pattern generator having an array of separatelycontrollable elements to modulate said unpolarized light beam to formone or more light beam shapes by selectively deflecting one or moreportions of the light beam away from the lens, substantially withoutabsorption of the light beam.
 32. The light projector of claim 31,wherein the light beam is at least partially transmitted to the objectof illumination in the one or more light beam shapes to project an imageon the object of illumination, the image being defined by theprogrammable light pattern generator and resembling a gobo pattern. 33.The light projector of claim 32, wherein the one or more light beamshapes is capable of being dynamically varied such that the imageresembles a plurality of gobo patterns.
 34. A light projector,comprising: a light beam source for generating an unpolarized light beamhaving an intensity suitable for lighting applications, said light beampropagating along a light beam path; a programmable light patterngenerator located to modulate said unpolarized light beam and having anaddressable array of elements, said programmable light pattern generatorbeing disposed in said light beam path and being illuminated by saidlight beam; a projection lens disposed in said light beam path andprojecting an image of said programmable light pattern generator asilluminated by said light beam; an active heat control system forprotecting said addressable array from the heat generated by said lightbeam; and a source of control signals connected to said addressablearray to control the states of said elements to modulate said lightbeam, wherein each of a plurality of elements of said addressable arrayof elements can be individually driven to one of a plurality of states,comprising: one state in which light incident on said element iscollected by said projection lens and projected as at least a portion ofsaid image; and another state in which incident light on said element isscattered at least in part by reflection and effectively prevented frombeing collected by said projection lens and projected as at least aportion of said image.
 35. The light projector of claim 34, wherein theprogrammable light pattern generator is located to form a light beamshape, and wherein the light beam is at least partially transmitted tothe object of illumination in the light beam shape to project the imageon an object of illumination, the image resembling a gobo pattern. 36.The light projector of claim 35, wherein the light beam shape is capableof being dynamically varied such that the image resembles a plurality ofgobo patterns.
 37. A light beam shape altering device, comprising: alight beam source for generating a light beam having an intensitysuitable for lighting applications; a projection lens disposed toreceive and transmit said light beam to an object of illumination; and aprogrammable light pattern generator having an array of selectivelycontrollable elements defining a light beam shape transmitted throughthe projection lens to an object of illumination; and each of theelements comprising a light beam direction deflection device selectivelydeflecting, instead of blocking, at least a portion of said light beamin a direction away from the lens to form one or more opaque areas in atleast a portion of the light beam, substantially without absorption ofthe light beam and resulting heating of said programmable light patterngenerator.
 38. The light beam shape altering device of claim 37, thelight beam is at least partially transmitted to the object ofillumination in the light beam shape to project an image on the objectof illumination, the image being defined by the programmable lightpattern generator and resembling a gobo pattern.
 39. The light beamshape altering device of claim 38, wherein the light beam shape iscapable of being dynamically varied such that the image resembles aplurality of gobo patterns.
 40. A light projector, comprising: a lightbeam source for generating an unpolarized light beam having an intensitysuitable for lighting applications, said light beam propagating along alight beam path; a projection lens disposed in said light beam path andprojecting an image of said programmable light pattern generator asilluminated by said light beam; a programmable light pattern generatorlocated to modulate said unpolarized light beam and having anaddressable array of elements, said programmable light pattern generatorbeing disposed in said light beam path and being illuminated by saidlight beam, wherein each of a plurality of elements of said addressablearray of elements can be individually driven to one of a plurality ofstates, comprising: one state in which light incident on said element iscollected by said projection lens and projected as at least a portion ofsaid image; and another state in which incident light on said element isscattered at least in part by reflection and effectively prevented frombeing collected by said projection lens and projected as at least aportion of said image; an active heat control system for protecting saidaddressable array from the heat generated by said light beam; and asource of control signals connected to said addressable array to controlthe states of said elements to modulate said light beam.
 41. The lightprojector of claim 40, wherein the programmable light pattern generatoris located to form a light beam shape, and wherein the light beam is atleast partially transmitted to the object of illumination in the lightbeam shape to project the image on an object of illumination, the imageresembling a gobo pattern.
 42. The light projector of claim 41, whereinthe light beam shape is capable of being dynamically varied such thatthe image resembles a plurality of gobo patterns.